Mixing yellow and blue paint produces green, which surprises people taught that mixing light works differently.

The longer version

Paints work by subtraction. Yellow pigment absorbs blue wavelengths and passes red and green; blue pigment absorbs red and passes green and some blue. Mix them and green is the only band both leave alone, so green is what comes back to the eye.

That is why painters avoid mixing everything at once: each added pigment removes more of the spectrum, and a muddy mix drifts toward dark brown or gray. Children first meet additive mixing on screens and subtractive mixing in paint, and the two rules genuinely contradict each other. Printing is subtractive, which explains the different primary set.

Where this entry sits

These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.